The present invention relates to the field of musical instruments, and more particularly, in the field of stringed musical instruments it relates to improved structure in a nut assembly for string support that provides adjustment for string clearance to satisfy the string setup demands of the conventional guitar family as well as the more exacting demands of instruments designed to be played with a two-handed string-tapping technique. such as The Chapman Stick.
In stringed instruments such as guitars, typically a neck portion including a fingerboard, extends from a body portion to an integral headstock which carries tuning pegs and their mechanisms. The strings are stretched over two basic support points; the first known as the bridge, located in the body region, and the second known as the nut, located between the fingerboard and the headstock. The distance between these two support points, in conjunction with the string tension and mass, determines the vibrational resonant frequency and thus the musical pitch of an open string.
The player can increase the pitch by stopping the string, i.e. pressing it against the fingerboard, which may be smooth and fretless as in a violin, but more commonly in the lute/guitar family, made as a fretboard with transverse frets spaced to form the chromatic musical scale. To raise the pitch a semitone from open tuning the player finger-stops the string at the first fret by placing a finger on the string between the nut and the first fret and pressing it against the fret, thus moving the second support point closer to the bridge, which remains fixed as the primary support point. This shortens the vibrational string length and increases the pitch a semitone higher than the open string pitch. The player then plays the note by picking, plucking or strumming the string with the other hand with a velocity that determines the initial amplitude and loudness, then the note rings with diminishing amplitude until it dies out at the end of the sustain time.
In the case of tapping technique, by quickly and cleanly pressing a string against a fret and holding it there: the burst of energy imparted as momentum by the velocity of the initial displacement becomes converted to vibrational energy that determines the initial amplitude and loudness, then, as in conventional technique, the note rings with diminishing amplitude until it dies out at the end of the sustain time. Since the tapping technique eliminates the need to pick, pluck or strum the strings, both hands can be dedicated to playing notes on the fretboard, more strings can be utilized, typically eight, ten or twelve, and thus the player""s versatility and virtuosity are potentially doubled. For the tapping technique the demands for accurate string-to-fret spacing are more exacting, therefore, prior to the present invention, all Chapman Stick instruments were made with individual string height adjustments at the nut.
Conventional fretboards are typically made with a transverse convex curvature, while the Chapman stick is made flat; in either case each fret is made to be constant in height above the fingerboard. The two string support points are initially set up for height to provide a desired xe2x80x9cactionxe2x80x9d as determined by the spacing between the bottoms of the strings and the tops of the frets. This is usually made different for different string sizes, and is usually set as low as possible for ease of playing, while avoiding any buzzing due to vibrating strings coming into contact with higher frets. There is almost always a succession of strings of different diameters, which all need to be accurately spaced from the frets for optimal overall playing action, for which both the bridge and the nut must be set accurately.
The bridge establishes the height and inter-string spacing at the first support point, which principally determines the action over the entire fretboard. When a string is finger-stopped at any fret, the bridge height for that string sets the fret-to-string clearance at all higher frets, and since these all face the vibrating portion of the string, they require sufficient clearance. In many guitars the bridge height is adjustable by rotating a pair of thumb-finger screw adjustment wheels, one at each end of the bridge. In some professional-quality guitars and in all models of the Chapman Stick, the bridge is equipped with individual height adjustments for each string.
At the other support point, in both conventional guitars and tapping type instruments the height of the nut support point also affects the overall action importantly, since it affects the amount of string displacement required to finger-stop or to tap a string at a fret, particularly toward the nut end. However, the string-to-fret clearances are affected by nut height only when the string is played open: with a string finger-stopped at a fret, clearance for the vibrating string portion depends entirely on the bridge height. Thus a guitar requires the nut to made high enough to prevent vibrating string contact with any fret, particularly the first fret.
A higher action setting makes finger-stopping and tapping more difficult due to the geometrically required stretching and vertical bending of the strings, particularly at the first fret.
With the string-tapping technique, open strings are normally not played, and generally the maximum vibration amplitude is smaller on all strings than with conventional guitar playing techniques. Thus, for tapping-type instruments, it has been found possible and desirable to set up the instrument for much lower action: in particular the nut can be set to make the first fret-to-string spacing much closer on all strings, which greatly enhances the ease of playing with the tapping technique, particularly at the first and lower frets.
Typically the guitar nut is made from a hard material such plastic, bone or metal, and is placed in a fixed location, typically held with adhesive, providing only a general purpose string height setting that is not user-adjustable.
The nut is typically configured on top with a series of notches known as saddles, one for each string, that function to constrain the strings laterally, to keep them spaced apart uniformly, and to support them at the correct height above the first fret to set the desired string-to-fret clearances.
A greater clearance must be set between the bottoms of the strings and the tip of first fret for larger strings due to their increased vibrational excursions. The strings typically vary in diameter, ranging in a sequence from thinnest to thickest along the fret to provide a single tuning group.
On guitars, the saddle notches are usually saw-cut to be approximately rectangular in cross-section; they may be made different in width to laterally constrain different sized strings and different in depth for different fret clearances requirements of different sized strings. These variations are difficult to standardize, and restrictive with regard to altered tunings and/or string gauges, leading to substantial burdens, problems and costs in original manufacture, field use, maintenance and repair, often requiring costly, tedious sawing and filing operations that must be performed manually on individual saddle notches by skilled technicians attempting to obtain optimal playing action. Excessive sawing or filing can destroy the nut due to loss of sufficient string clearance at the first fret, and the nut would then have to be removed and replaced with a new one.
Despite these shortcomings, the conventional fixed nut system is considered to be cost-effective and generally satisfactory for many basic conventional stringed instruments with only four or six strings in a single tuning group. However, it may become troublesome in instruments with eight or more strings, particularly if the strings are arranged in two or more tuning groups. For example, in The Chapman Stick, standard models have ten strings divided into two tuning groups of five; very low playing action, i.e. close string-to-fret spacing, is particularly important for the string tapping technique.
U.S. Pat. No. 4,304,203 by Siminoff, for an ADJUSTABLE NUT FOR STRINGED MUSICAL INSTRUMENTS discloses individual string height adjustment implemented by individual saddle pieces, one for each string (or pairs thereof) each threaded into a common nut bar.
U.S. Pat. No. 3,429,214, by Jones, for a NUT-MOUNT FOR FINGERBOARDS discloses a common nut bracket to which are attached individual string nuts and support members, one for each string, individually adjustable with a set screw for string height, with saddles formed by separate side guides and low-friction cylindrical roller nut mounting to allow strings to return to normal tension after release of playing pressure.
U.S. Pat. No. 3,599,524, also by Jones, for a NUT-MOUNT FOR STRINGED MUSICAL INSTRUMENT FINGERBOARDS discloses individual string nuts with structure similar to the aforementioned patent, with the further capability of adjustably offsetting the individual nut supports longitudinally along the strings for correcting the tuning of fretted and fretless instruments.
U.S. Pat. No. 5,173,565 for ROLLER BRIDGE SADDLE by Gunn discloses a xe2x80x9croller string guide for a musical instrument, such as a roller bridge saddlexe2x80x9d, with a special rigid seated bearing structure to preserve vibrational energy and enhance sustain. The saddle notch provided by the roller is shown configured with a V-shaped cross-section.
U.S. Pat. No. 5,260,504 STRING SUPPORT FOR STRINGED INSTRUMENT by Turner discloses a nut and/or saddle that supports each string being on a pair of freely-rotatable ball bearings, allowing unrestricted forward and backward movement for maintaining the pitch of the string.
Similarly U.S. Pat. Nos. RE36,484 to Turner, U.S. Pat. No. 2,191,776 to Schreiber, U.S. Pat. No. 2,959,085 to Porter, U.S. Pat. No. 4,709,612 to Wilkinson and U.S. Pat. No. 5,438,901 to Sperzel disclose nut assemblies that utilize rotatable supports such as balls or rollers for low friction including means such as cams, rollers of different diameter, and set screws for individually adjusting the string heights.
Providing individual height adjustment for each string or string pair is complex and costly to the extent that it has never become popular in the stringed instrument marketplace, where the economical one-piece nut structure has remained conventional and practically universal despite its shortcomings.
Many of the foregoing cited patents address concern regarding longitudinal movement of the strings at the nut, proposing as the solution anti-friction string support at the nut, such as pulleys, rollers or hall bearings. This concern pertains to conventional instruments under hard playing conditions and/or frequent manipulation of string tension by string-bending or operating a tension-lever known as a xe2x80x9cwhammy barxe2x80x9d.
In the field of instruments for string-tapping techniques, the playing method does not cause any appreciable movement of the strings on the nut, so such friction has not been found to be a matter of concern.
Similarly the need for individual or overall longitudinal adjustment at the nut addressed by some of the cited patents does not apply to the string-tapping technique: because notes on the open strings cannot be initiated by tapping the string against a fret, the open string notes are not normally played, instead, the lowest available note played on each string is played by tapping it onto the first fret. A damper is usually provided, located between the nut and first fret, to prevent unwanted ringing of open strings. Furthermore, in instruments for string-tapping technique the nut action can be set low and the nut can be located at the ideal fixed point with no need for longitudinal adjustment.
In general, most prior art is directed to problems and solutions that are not applicable to the string-tapping technique, while failing to address the special requirements of the string-tapping technique. Yet solutions addressing these requirements, such as in the present invention, are potentially applicable as well to guitars and other stringed instruments played in the conventional manner.
It is a primary object of the present invention to provide an improved nut assembly that provides satisfactory string support and enables simple adjustment of string-to-fret clearances and overall playing action in stringed instruments such as guitars as well as instruments made to be played with string-tapping technique.
It is a further object in the configuration of the nut to make the string-support saddle notches uniform in cross-sectional shape to facilitate manufacturing.
It is a further object to provide a nut assembly wherein a single nut unit can satisfactorily accommodate up to eight strings in a single tuning group.
It is a further object of the invention to provide an improved nut assembly that accomplishes satisfactory string-to-fret spacing and overall playing action for special stringed instruments having more than eight strings, particularly where the strings are arranged in two tuning groups.
It is a further object that the improved nut assembly be made to provide string height adjustment capability that satisfies the exacting requirements of very close string-to-fret clearance for stringed instruments designed to be played with two-handed tapping technique, such as The Chapman Stick.
It is a further object to make the nut assembly a neutral environmental element that is adaptable and reconfigurable to all tunings and string gauges and to both regular and reversed group tuning sequences, both in original manufacture and in the field.
It is a still further object to make the nut assembly, or each of the two nut units thereof, easily adjustable for height at each end, in infinite gradations.
The abovementioned objects have been accomplished by the present invention of an improved nut assembly that can be deployed as a single nut unit or two nut units aligned end-to-end. Each nut unit is provided with a pair of adjustable support legs located near the ends of the nut, made to bear the pressure from the stretched strings to the underlying neck region.
In conjunction with these two adjustable support legs, the nut requires stabilization to hold it generally perpendicular to the landing, to constrain it from rotating or shifting in any direction in a horizontal plane, and for pre-retention, i.e. retaining the nut in the absence of strings, for manufacturing and servicing purposes.
In a primary embodiment, the two support legs are implemented as a pair of set screws, engaged in threaded holes near the ends of a main nut block, adjustable from above, and extending downwardly to bear on the surface of a flat landing which is typically machined in the neck, extending toward the first fret region and forming a vertical riser that steps up to the fingerboard level. The set screws function as adjustable support legs set to hold the bottom surface of the nut block raised above the landing surface by a small space that ensures adjustability.
In the primary embodiment, the nut block is stabilized for orientation perpendicular to the fingerboard and horizontal constraint by a stabilizing flange, extending integrally from the bottom region of the nut block forming a cantilever directed toward the body of the instrument. The stabilizing flange is secured to a central region of the neck landing in a xe2x80x9cfloatingxe2x80x9d manner utilizing a thick compressible member, such as a washer of rubber-like material or spring spacer made of metal, held under compression by an adjustable fastening screw traversing the flange and spacer and threadedly engaging the neck/fingerboard. The two set-screws and the fastening screw holding the flange thus form a triangular nut support system. Stabilization against rotation is provided by abutting the edge of the flange against the vertical riser at the edge of the landing.
The string support channels are preferably made in a V-shape that can accommodate all sizes of strings with precise center-to-center spacing assured; furthermore the V-shape automatically provides greater fret clearance for the larger vibrational excursion of the large lower frequency strings.
For a stringed instrument with more than six strings and/or with the strings arranged in two tuning groups, and particularly for stringed instruments designed to be played with a two-handed tapping technique, such as The Chapman Stick, two of the improved nut units can be deployed end-to-end, each dedicated to a tuning group: these can each be adjusted independently by the two set screws along with the third stabilizing screw adjustment for optimal string-to-fret clearance.
The string spacing between the two string tuning groups can be made uniform with the other strings or else increased by spacing the two nut units further apart.
In alternative embodiments, the nut block may be made without the stabilizing flange, and the stabilizing functions may be provided by various fastening configurations located in within the immediate region of the nut block. Hardware for stabilization may be located in line with the adjustment screws immediately beneath the nut ridge line. The perpendicular orientation can be stabilized by utilizing a pin or fastening screw that is closely constrained in sufficiently long holes both the nut block and the neck, while the anti-rotational stabilization can be implemented by abutting the nut block against the step riser of the landing, or by utilizing two doubly-constrained pins, fastening screws or set screws.